Method of making hollow articles



Feb. 4, 1936. w. SCRIMGEOUR 0 Filed March 27. 1935 s Sheets-Sheet 1 Feb.4, 1936. w. SCRIMGE'OUR 2,029,503

METHOD OF MAKINQ HOLLOW ARTICLES Filed March 27, 19:55 :5 Sheets-Sheet 2Feb, 4, 1936 W. SCRIMGE OUR METHOD OF MAKING HOLLOW ARTICLES Filed March27, 1935 3 SheetsSheet 5 gig Patented Feb. 4, 1936 UNITED STATES PATENTOFFICE 10 Claims.

This invention relates to methods of making hollow articles,particularly poppet valves for internal combustion engines, by forgingoperations.

The method which is described in my prior patent, No. 1,992,245,includes the punching of the closed end of a counterbored blank to forma rounded end wall, swaging the tubular part 01' the blank to form anelongated stem, and stamping the closed or ball end to form the! hollowhead. While this method is entirely practical, the machining of thecylindrical blank and the swaging down of the stem are'relatively slowand expensive operations.

An object of theinvention. is to provide improved and economical methodsfor forging onepiece hollow articles. An object is to provide a methodof forming metal blanks or shells which can be forged to produce hollowarticles having ends of substantially different diameters. Furtherobjects are to provide methods of forging hollow valves by punching androlling. I

These and other objects and advantages of the invention will be apparentfrom the following specification when taken with the accompanyingdrawings, in which: i

Fig. 1 is a horizontal section, as taken on line l-l ofFig. ,2, of aneconomical form of'die in which the first operation is performed;

Fig.2 is avertical central section of the die;

Fig. 3 is a vertical section, taken at right angles to Fig. 2, throughthe die and punch;

Fig. 3a is a fragmentary section showing an alternative construction forthe base of the die;

Fig. 4 is a side elevation of the metal blank;

Fig. 5 is a fragmentary section, similar to Fig. 3, illustrating theremoval of the punched blank from the die;'

Figs. 6a to 6e, inclusive, are fragmentary sections showing alternativeshapes for the die;

' Fig. 7 is a fragmentary plan view of apparatus for rolling down thestem portion of the valve blank;

Fig. 8 is a vertical section on line 8-8 of Fig. 'I;

Fig. 9 is a vertical section on line 9-9 of Fig. 8;

Figs. 10' and 11 are schematic views illustrating successive rollingoperations upon the blank;

Fig. 12 is a sectional view through dies for forming the valve head; and

Fig. 13 is a side elevation of a valve blank as it leaves thehead-forming dies.

The metal commonly employed for the manufacture of hollow valves issteel which contains nickel, tungsten and chromium or the like insuchquantity as to provide high resistance to corrosion and damage byheat. Steels of this type are somewhat plastic at high temperature butexcessive wear on the dies has characterized prior attempts to forgehollow shells having a diameter approximating that of the finished 5valve head. The flow of the hot steel under heavy pressure alongthecurved and/or junction surfaces of the dies results in a pitting or wearof the die surfaces which renders them useless after a comparatively fewoperations. Shaping l0 methods and dies which have been employed withrelatively plastic metals and alloys have proved to be unsatisfactory inthe working of corrosion-resistant steel and similar hard metals.

According to this invention, a cylindrical blank 15 of hot steel ispunched in dies which are so shaped as to avoid destructive wear. Asshown in Figs.

1 to 3, a heavy die'block l is counterbored from the top to provide aseat for the die 2 which has an unbroken or continuous inner wallmeeting 20 the edge of the shape-imparting surface 3 of an end diemember 4 which is held securely against the die 2 by a wedge 5. The die2 is locked in place by pins 6 which extend through the block I. Theblock I is provided with integral ears I for 25 attaching the block tothe table of .a press or, as shown in Fig. 3a, the base of the block maybe formed as a dovetail 'l' for this purpose.

The movable head 8 of the press carries a punch 8 which has a roundedlower end for en- 30 tering the die. The punch is tapered to provideclearance and the inner wall of the die also tapers slightly towards thetop. The starting material for forming the valve is a short cylindricalblank III which is of such diameter as to 35 drop freely into the die 2when hot, and of such length as to provide sumcient material for a valveof the desired size and length. The blank is solid and has a diametersubstantially less than that of the finished valve head but is muchgreat- 4 er than the desired stem diameter.

It will be noted that the surfaces of die members 2 and 4 meet at themaximum diameter section of the shape which is to be imparted to theblank and that there will be a flow of metal tov wards, but not along,this junction of the dies. The cylindrical blank i0 is punched byrapidly forcingthe punch 9 into and withdrawing the same from the hotblank. This may be accom A plished in one or a pluralityof strokes ofthe 5 upper head 8 but, in any event, the punch 9 is quickly withdrawnfrom the blank before it can expand and lock to the hot steel. Thetapering of the die 2 facilitates this withdrawal of the punch as theslightly conical form of the die locks 55 the punched blank I 0 againstupward movement. Separate members may be used to hold the blank I0 asthe punch 9 is lifted but, in general, separate holding members are notrequired when the die 2 is appropriately shaped. Upon removal of thepunch 9, the wedge 5 is shifted to the right, Fig. 2, to permit removalof die member 4, and the blank [0' is then forced downwardly out of die2 by a stripper II.

The dies shown in Figs. 1 to 3 will transform the cylindrical blank l0,Fig. 4, into a tubular shell l0, Fig. 3, of slightly larger diameter andhaving a rounded end wall of about the thickness Dies 2a and 4a of Fig.6a are of the side walls. cut back at their meeting edges to form agroove l2 which will result in a thickened rib or bead at the base ofthe rounded end of the tubular shell. As shown in Fig. 6b, the lower endof die 2b may be flared outwardly to form a conical surface l3 thatmeets the rib-forming surface of die 4a. In the form shown in Fig. 6c,the die members 2c, 40 may have meeting surfaces It that form anenlarged globular head on the blank. This form is desirable whenrelatively large diameter valves are to be formed from small diameterstock. Another die formation appropriate for large valves is shown inFig. 6d. The lower end of the slightly conical bore of die 2d is Smalldiameter valve heads and other hollow articles which are to haveportions rolled down to smaller sizes may be made from punchings in thesimple dies 2e, 4c of Fig. 6e. The lower die 4e has a centralcylindrical recess H but has a flat surface l8 meeting the slightlyconical surface IQ of die 2e.

The tubular shell III" that is stripped from the die 2 is transferred,either directly or after reheating, to the pressure rolling apparatusshown in Figs. 7 to 9. A pair of rolls 20 are mounted in brackets 2| ona supporting base 22 and are rotated in the same direction by a shaft 23and gearing 24. An idler roller 25 is carried by the moving head 26 ofthe pressure piston 21, the head having a dovetail extension 28 that isslidable on the base 22. The movement of the head 26 and idler roll 25is controlled by the admission of pressure fluid to the cylinder 23. Theshaping rolls 2!), 25 have the same profile and each is reinforced by aset of idler or backing rolls 30. A pin or mandrel 3| is arrangedparallel to the axes of the rolls to receive the blank l0 and supportthe same during the initial stage of the rolling operation.

The blank I0 is dropped over the mandrel 3| and pressure fluid issupplied to chamber 29 to force the idler roll 25 towards the drivenrolls 20. The blank l0 rotates on mandrel 3! during the initial workingof the tubular section of the blank and the mandrel is then lowered bymeans, not shown, into the position shown in Fig. 10. The upper ends ofthe shaping rolls are concave and shape the end portion Illa of theblank to approximately globular form and lower sections of the rollsreduce the adjacent portion lllb of the blank to a cylinder of smalldiameter. The lower ends of the rolls taper down to form the flaring endsection we of the blank. By thus working down the intermediate portionof the blank, it is not necessary to provide a separate support to takeup end thrust as the axial pressures exerted upon the blank by the rollsare substantially balanced and there is no tendency for the blank tomove axially out of the rolls. The flaring section lllc of the blank isthen rolled to form an extension of the stem section lflb in another setof rolls 20 which have upper ends shaped to engage the globular endsIlla. The lower ends of the blanks are preferably reheated before thisoperation, and the heads Illa are relatively cool.

The bore of the stem may be completely closed during the rollingoperation, as shown in Fig. 11, or a mandrel of softer metal could beleft within the blank to form a soft core that could be readily drilledout in the subsequent finishing of the valve. The head Id of the valveis formed, in known manner, by die forging the globular end section. Theblank such as shown in Fig. 11 is placed in the split die members 32 andis pressed axially by die 33 to flatten the rounded end and shape themetal to the form of the recessed ends of the dies.

As compared with the process described in my prior patent, the presentinvention has the advantages of speed and economy in manufacture. Thepunching of the cylindrical blank to form a tubular shell avoids loss ofmetal by machining and is more rapid and less expensive than the priorcounterboring operation. It is also economical to roll down the stemsection of the blank as this operation does not require the high skillthat must be employed in swaging down. the blank. Automatic controldevices of known design may be used with the pressure cylinder toregulate the rate and extent of movement of the idler roll, and thefactor which the operator is required to judge is that of thetemperature of the blanks which are placed between the rolls. Forgedvalves ready for machining can be produced rapidly and with practicallyno defects so long as the temperature ranges for the differentoperations are properly selected and maintained. Wear on the dies of thepunching machine is comparatively low as the metal does not flow acrossbut towards the junctions of the die members.

It is to be understood that there is some latitude in the particulardesign of the dies and rolls, and that the form of the blank atdifferent intermediate stages of the forging operations may thereforevary somewhat from the blanks illustrated herein. 7

I claim:

1. The method of forming a hollow valve which comprises punching a solidcylindrical blank to form a hollow tube having an end wall ofsubstantially the thickness of the side wall thereof, working down thetubular portion of the blank from a portion adjacent said end wall toform an elongated stem, and pressing the end wall axially to form avalve head.

2. The method of forming a hollow valve which comprises punching acylindrical metal blank against an end block and restricting lateralflow of the metal by a die having a continuous circumferential wall,whereby metal displaced by the punch flows rearwardly along the same toform a tubular portion extending from the end wall formed between thepunch and the end block, working down the tubular portion into anelongated stem, and shaping the end wall portion into a hollow valvehead of larger diameter than the stem.

3. In the manufacture of hollow valves, the steps which comprise forcinga punch into a solid blank positioned in a stationary die to form ashell having a rounded end, rolling down the tubular part of the shellto form a stem, and diestamping the rounded end portion to form a hollowhead.

4. In the manufacture of hollow steel articles, the method of forming atubular shell which comprises forcing a punch into a solid cylindricalsteel blank resting-upon an end die having an approximatelyhemisphericalrecess, and restricting lateral flow of the steel by a diehaving a continuous inner circumferential wall, thereby to form atubular shell having a closed hemispherical head.

5. The process of forming a tubular shell from which a hollow-head valvemay be forged, which comprises placing a heated metal blank in a diehavingan unbroken end surface meeting an unbroken circumferentialsurface tapering inwardly in a direction away from the end surface,forcing a punch into said blank to effect a flow of metal into closecontact with said surfaces, withdrawing the punch, separating the endsurface portion of the die from the punched blank, and forcing thepunched blank from the other of said surfaces by pressure applied in thedirection of the punching pressure.

6. The method of forming a valve which comprises placing a billet in adie having a continuous inner circumferential wall meeting theshape-defining surface of an end block, forcing a punch towards the endblock and into the blank to form a tubular blank having a closed endwall, working down the tubular portion of the blank to form a stemsection, and pressing said end gall axially of the stem to form a hollowvalve ead.

7. The method of forming a valve which comprises placing a billet in adie having a continuous inner circumferential wall meeting the shapedefining surface of an end block, forcing a punch towards the end blockand into the blank to form a tubular blank having a closed end wall,rotating the blank about its axis and pressing radially upon the tubularportion thereof to form a. stem section, and pressing said end wallaxially of the stem to form a hollow valve head.

8. In the manufacture of hollow head valves, the steps which comprisepunching a solid blank to form a tube having one end wall, forming thetube from a point adjacent the end wall into a smaller diameter sternportion by rotating the tube about its axis while subjected to radialpressure from a plurality of circumferentially spaced rolls, anddie-forging the end wall and adjacent portion to form a hollow valvehead.

9. In the process of forming hollow one-piece articles, the stepswhich'comprise'punching a cylindrical billet to form a tube having oneend wall, and rotating the tube about its axis while subjected to radialpressure from a plurality of circumferentially spaced and rotatablerolls, thereby to reduce the diameter of and to elongate the tube at theregion where such radial pressure is applied.

10. In the process of forming hollow one-piece articles, the steps whichcomprise punching a solid cylindrical metal blank to form a tubularshell having a. rounded end wall, working down the tubular portion ofthe shell without reducing the diameter of the rounded end, and pressingthe rounded end to form a hollow valve head.

WILLIAM SCRIMGEOUR.

